This means both parents must be Aa. 17.

So the mother could be ‘Aa’ or ‘AA’. Thank you so much, hope they help. Post was not sent - check your email addresses!

During our four-year journey with CIE, we’ve managed to grab several Cambridge Learner Awards, including one Top in World and five Top in Country (India) awards. Start studying IGCSE Edexcel Biology - Monohybrid Inheritance. I hope you find this useful! Hope what's there helps anyway.. :)I do actually have more notes than is posted, and these can be purchased by buying my IGCSE Notes sets. Genes are always at the same position (locus) on homologous chromosomes.)

We cannot, however, deduce the mother’s genotype from the given information.In a similar fashion, we can work out the genotypes for the final family.If you have any queries, complaints or suggestions, feel free to comment, or write to us at:The IGCSE AID Team is based in the little state of Kerala in South India.

This is because heterozygous individuals possess different alleles of a gene, so their offspring may not be identical.e.g.

:)Note: This blog will no longer be updated, but I will read emails.So, I've finished IGCSEs but I'm leaving my blogs open in hopes that they help people.

Home › Biology Revision › CIE IGCSE › Topic 17 – Inheritance.

This blog is no longer updated as I've finished IGCSEs in 2012.

A genetic diagram consists of the parents gamets (according to their genotype) and their possible offspring: (B and b represent an allele for a gene) One is affected and the other two are unaffected.We know that the father has the genotype ‘aa’. This means both parents can not be AA – at least one of them is Aa.In the second generation, since the affected : unaffected ratio is 1 : 1, it is most likely that one parent is AA and the other is Aa. He carried out breeding experiments on garden peas (Pisum sativum). Inheritance. It is ‘a’ that codes for albinism, making albinism a recessive disorder.At the top of the chart, in the first generation, both male and female are unaffected, so they could be AA or Aa.When we look at the next generation, we can see that there are both affected and unaffected offspring. For his experiments, Mendel selected several varieties of garden pea plants with one pair of contrasting characteristics or traits such as: 

)A is dominant, so wherever A is present, the organism will be normal.This means one of the parents is normal and the other an albino, and all the offspring are normal.Here’s a cross between two F1 organisms.

This learning objective is just a definition you need to memorise!Pure-breeding is when a group of identical individuals produce offspring with the same phenotype.As homozygous organisms all have the same alleles, their offspring must have the same alleles.

So we know that their genotype is either AA or Aa.First, let’s look at the first family from the left. Written explanations are as simple as possible as a lot of my pupils are EAL learners. T, and the recessive allele is usually denoted using a small letter, e.g. If one of them was AA, and the other Aa, the children would either be AA or Aa, so none of them would be affected. two individuals with genotypes AA and AA will definitely produce offspring with the genotype AA.That means two identical homozygous individuals that breed together will be pure-breeding.Note: in the above example, ‘A’ is shorthand for the dominant version of a particular allele. Key vocabulary is highlighted throughout. I've finished IGCSEs and the IB but I hope these blogs help people with their IGCSEs anyway!!

E.g.

However, this family has one affected child. Genes are always at the same position (locus) on homologous chromosomes.) But I've reworded what I can. Mendel's monohybrid experiments-named after Gregor Mendel, a 19th century Austrian monk who first explained how heredity might work.

I may sometimes reply to questions if you comment or email me, but not guaranteed. These have been made according to the specification and cover all the relevant topics in the syllabus for examination in May/June as well as October/November and March. However, the child has a father that is homozygous recessive, so she must have inherited at least one ‘a’ allele from her father, meaning that we can deduct that the child’s genotype is Aa. Their genotypes are aa.The other offspring are white, and so unaffected.

Learn vocabulary, terms, and more with flashcards, games, and other study tools. Therefore, we know the mother is Aa.The affected child is aa, and since the mother is Aa and the father aa, we know the unaffected children must be Aa.The mother and father are unaffected, so are either Aa or AA. They have both unaffected and affected children, so at least one of them must carry the ‘a’ allele. The affected child is aa and the unaffected child can either be Aa or AA.The father is affected, so he has genotype aa. A monohybrid cross involves the crossing of individuals and the examination of one (mono) character (flower colour, pod shape...) and different (hybrid) traits (red colour, white colour) in their offspring.

It is very interesting!Please tick a box showing your reaction, and any feedback is appreciated.